JP2018162191A - Ceramic sintered body and wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic sintered body having high mechanical strength and chemical resistance and excellent high frequency characteristics, and a wiring board using the same. SOLUTION: A ceramic sintered body in which a composite phase of an alumina crystal phase 1a and a mulite crystal phase 1b is used as a main crystal phase 1 and a canoeite-based crystal phase 5 is contained in a grain boundary 3 of the main crystal phase 1. The alumina crystal phase 1a is surrounded by a mullite crystal phase 1b spread out in a matrix, and the wiring substrate is an insulating substrate composed of the above ceramic sintered body and a conductor provided on at least the surface of the insulating substrate. A wiring board including layers. [Selection diagram] Fig. 1

Description

  The present disclosure relates to a ceramic sintered body and a wiring board using the same.

  Conventionally, a semiconductor element is used as an active element for communication in electronic devices such as optical communication and wireless communication. In this case, the wiring board for mounting the semiconductor element for communication is also required to cope with high frequencies. As a wiring board for meeting such demands, a board using mullite as an insulating base has been proposed (see, for example, Patent Document 1).

JP 2010-93197 A

  However, mullite originally has problems such as low mechanical strength and low chemical resistance depending on the composition of the insulating substrate.

  Therefore, an object of the present disclosure is to provide a ceramic sintered body having high mechanical strength and chemical resistance and excellent high frequency characteristics, and a wiring board using the ceramic sintered body.

  The ceramic sintered body of the present disclosure includes a composite phase of an alumina crystal phase and a mullite crystal phase as a main crystal phase, and a canoite-based crystal phase at a grain boundary of the main crystal phase.

  A wiring board according to the present disclosure includes an insulating base composed of the ceramic sintered body and a conductor layer provided on at least a surface of the insulating base.

  According to the present invention, a ceramic sintered body having high mechanical strength and chemical resistance and excellent high-frequency characteristics and a wiring board using the same can be obtained.

It is a cross-sectional schematic diagram of the ceramic sintered compact of this embodiment.

  FIG. 1 is a schematic cross-sectional view of a ceramic sintered body according to the present embodiment. The ceramic sintered body of the present embodiment includes the alumina crystal phase 1 a and the mullite crystal phase 1 b as the main crystal phase 1, and includes the canoite-based crystal phase 5 at the grain boundary 3 of the main crystal phase 1. Here, the main crystal phase 1 refers to a case where the combined ratio of the alumina crystal phase 1a and the mullite crystal phase 1b is 60% by mass or more.

  According to the ceramic sintered body of the present embodiment, since the main crystal phase 1 is a composite of the alumina crystal phase 1a and the mullite crystal phase 1b, the alumina crystal phase 1a exists alone in the main crystal phase 1. By including the mullite crystal phase 1b, the relative dielectric constant, which is one of the dielectric characteristics that dominate the high frequency characteristics, can be reduced.

In addition, since this ceramic sintered body is a composite phase in which the main crystal phase 1 coexists with the alumina crystal phase 1a and the mullite crystal phase 1b as described above, the mullite crystal phase 1b is contained in the main crystal phase 1. The mechanical strength can be increased compared to the case where it exists alone.

  That is, this ceramic sintered body is mainly composed of the alumina crystal phase 1a that contributes to the mechanical strength and the mullite crystal phase 1b that contributes to the reduction of the relative dielectric constant.

  Further, since this ceramic sintered body includes the canoite-based crystal phase 5 at the grain boundary 3 between the main crystal phases 1, the ratio of the glass contained in the grain boundary 3 is reduced, and an amorphous phase such as glass is formed. Compared to the ceramic sintered body as the main phase, the chemical resistance of the grain boundaries 3 can be enhanced. The canoite-based crystal phase 5 is partially present in the mullite crystal phase 1b.

  In the ceramic sintered body described above, the average particle diameter of the alumina crystal phase 1a existing in the mullite crystal phase 1b is preferably 0.8 to 5.5 μm, particularly 0.8 to 3.8 μm. . As a result, various characteristics described above can be balanced and enhanced.

For example, when the ratio of each crystal phase contained in this ceramic sintered body is the ratio shown below, the insulation for a wiring board, which will be described later, is balanced by balancing all characteristics such as mechanical characteristics, dielectric characteristics and chemical resistance. It can be made useful as a substrate. For example, when the alumina crystal phase 1a is 15 to 82% by mass, the mullite crystal phase 1b is 20 to 82% by mass, and the canoite-based crystal phase 5 is 1 to 15% by mass, the mechanical strength (three-point bending strength) Is 232 MPa or more, the relative dielectric constant at 60 GHz is 8.2 or less, the dielectric loss tangent (tan δ) at the same frequency is 46 × 10 ⁻⁴ or less, and the weight reduction rate when evaluating chemical resistance is 0.12% by mass or less. A ceramic sintered body can be obtained.

  As shown in FIG. 1, the ceramic sintered body has a structure in which the mullite crystal phase 1b serves as a matrix and the alumina crystal phase 1a exists in the mullite crystal phase 1b via the grain boundary 3. Since the alumina crystal phase 1a having a high relative dielectric constant is surrounded by a mullite crystal phase 1b spread in a matrix, an increase in the relative dielectric constant can be suppressed even when there are many alumina crystal phases 1a. Here, the matrix form means a matrix structure having no clear grain boundary.

  The ceramic sintered body has a structure in which an alumina crystal phase 1a and a mullite crystal phase 1b, which are crystal phases, are bonded via a cananoite crystal phase 5. That is, the mechanical strength of the ceramic sintered body can be increased because of the structure in which the three types of crystal phases are bonded to each other.

  For this reason, even if the glass phase 7 is present at the grain boundary 3 of the ceramic sintered body, the glass phase 7 is in a state of being divided by the canoite-based crystal phase 5, so the glass phase 7 is also used in the chemical resistance test. Is less likely to elute, thereby improving chemical resistance.

Here, the canoite-based crystal phase includes, as elements, manganese, magnesium and silicon, and a metal oxide represented by (Mn, Mg) ₂ (Si ₂ O ₆ ) as a main constituent mineral. That is, the canoite-based crystal phase in this embodiment is intended to include even those in which the Mano, Mg, and Si constituting the kanoite have a non-stoichiometric composition.

Moreover, when the ratio of each crystal phase contained in this ceramic sintered body is limited as follows, the mechanical characteristics can be increased, and the relative dielectric constant and dielectric loss tangent can be decreased. Moreover, the weight reduction rate when evaluating chemical resistance can be reduced. For example, when the alumina crystal phase 1a is limited to 31 to 66 mass%, the mullite crystal phase 1b is limited to 30 to 65 mass%, and the cananoite crystal phase 5 is limited to 2 to 10 mass%, the mechanical strength (three-point bending strength) is 327 MPa. As described above, a ceramic having a relative dielectric constant of 7.9 or less at 60 GHz, a dielectric loss tangent (tan δ) of 28 × 10 ⁻⁴ or less at the same frequency, and a weight reduction rate of 0.09% by mass or less when chemical resistance is evaluated. A sintered body can be obtained.

Furthermore, when the proportion of the canoite-based crystal phase is limited to 2 to 7% by mass, the relative dielectric constant at 60 GHz is 7 with the above-mentioned mechanical strength (three-point bending strength) and chemical resistance maintained. .8 or less and the dielectric loss tangent can be made 18 × 10 ⁻⁴ or less.

  The ceramic sintered body described above is suitable as a high-frequency wiring board because it has high mechanical strength, excellent dielectric properties in a high-frequency region, and high chemical resistance. Specifically, when this ceramic sintered body is used as an insulating base and a wiring board having a conductor layer is formed on at least the surface of this insulating base, it can be used in a higher frequency region than a general-purpose alumina wiring board. The transmission characteristics are high, and the same quality as that of a general-purpose alumina wiring board can be obtained in terms of fitting and hermetic sealing.

Next, the ceramic sintered body of the present embodiment was specifically produced, and the characteristics were evaluated. First, as a raw material powder, an alumina powder having a purity of 99.5% by mass and an average particle size of 1.5 μm, a mullite powder having a purity of 99% by mass and an average particle size of 2.4 μm, a purity of 99.7% by mass and an average particle size An SiO ₂ powder of 1.5 μm, a Mn ₂ O ₃ powder having a purity of 99% by mass and an average particle diameter of 1.5 μm, and an MgCO ₃ powder having a purity of 99.5% by mass and an average particle diameter of 5.0 μm were prepared.

  Next, each raw material powder described above was mixed so as to have the ratio shown in Table 1. A ball mill was used for mixing the raw material powder. Alumina balls were used as the media.

  Next, an organic vehicle (a solution obtained by dissolving an acrylic binder in toluene) was added to the mixed powder to prepare a slurry. Thereafter, a green sheet having a thickness of 300 μm was prepared by a doctor blade method.

  Next, a predetermined number of the produced green sheets were laminated and heated under pressure, and then cut into a desired shape to produce a molded body that was the basis of the ceramic sintered body. Subsequently, the produced molded body was fired under the following conditions. Firing was performed at a temperature of room temperature to 600 ° C. in a nitrogen-hydrogen mixed atmosphere with a dew point of + 30 ° C., and then the dew point was changed to + 20 ° C. and held at 1400 ° C. for 1 hour. The size of the prepared ceramic sintered body sample was 40 mm in length, 5 mm in width, and 3.6 mm in thickness.

  Next, the following evaluation was performed about the produced ceramic sintered compact. The ratio of the alumina crystal phase, the mullite crystal phase, and the canoite crystal phase was determined by pulverizing the produced ceramic sintered body, performing X-ray diffraction, and performing Rietveld analysis. The number of samples was one. In this case, for those whose basic crystal structure is canoite, those whose lattice constant deviated from the original canoite were also identified as canoite-based crystal phases.

The average particle diameter of the alumina crystal phase was determined from a photograph of a cross section of the ceramic sintered body. Specifically, a sample cut from the produced ceramic sintered body was embedded in a resin, subjected to cross-sectional polishing, the crystal structure was observed using a scanning electron microscope, and a photograph was taken. Next, in the photograph taken, the alumina crystal phase present in the region of about 7000 μm ² was extracted, the particle size was measured by image analysis, and the average value was obtained. In the image analysis in this case, first, the outline of each alumina crystal phase was captured, and the area formed by the outline was once converted into a circle. Thereafter, the diameter was obtained from the circle, the diameter was made the particle size of the alumina crystal phase, and the average value was obtained from a plurality of samples to obtain the average particle size.

  The bending strength was processed by polishing the ceramic sintered body so as to have a size of 40 mm in length, 4 mm in width, and 3 mm in thickness. Also. C edge processing of the edge of the sample was also performed. Next, the prepared sample was set in an autograph, and a three-point bending test at room temperature (25 ° C.) was performed. The number of samples was 25 and the average value was calculated.

  Dielectric properties were determined by the cavity resonator method. A sample was prepared by processing a ceramic sintered body to have a length of 50 mm, a width of 50 mm, and a thickness of 0.5 mm. Next, the dielectric constant and dielectric loss (tan δ) of the prepared sample were measured in the frequency range of 55 to 60 GHz, and the dielectric characteristics in the vicinity of 60 GHz were calculated. The number of samples was three.

  Chemical resistance is the change in weight before and after immersion when 5 pieces of ceramic sintered bodies of length 40 mm, width 5 mm, thickness 3.6 mm are prepared and immersed in an acidic ammonium fluoride aqueous solution having a concentration of 10 g / L for 5 minutes. I asked for it. The calculation method of the mass reduction rate shown in Table 2 is “mass reduction rate = (“ mass before immersion of sintered body ”−“ mass after immersion of sintered body ”) /“ mass before immersion of sintered body ”× 100 ) ”.

As is clear from the results in Table 2, the sample (sample Nos. 1 to 7) having an alumina crystal phase of 15 to 82% by mass, a mullite crystal phase of 20 to 82% by mass, and a canoite-based crystal phase of 1 to 15% by mass. 9-14, 16 and 18-20), the mechanical strength (three-point bending strength) is 232 MPa or more, the relative dielectric constant at 60 GHz is 8.2 or less, and the dielectric loss tangent (tan δ) at the same frequency is 46 × 10 ^{−. 4} or less, the rate of change in weight when chemical resistance was evaluated was 0.12% by mass or less. All of these samples had a crystal structure surrounded by a mullite crystal phase in which the alumina crystal phase spread in a matrix.

Moreover, about this ceramic sintered compact, the sample (sample No. 3-5 which limited the alumina crystal phase to 31-66 mass%, the mullite crystal phase to 30-65 mass%, and the canoite type | system | group crystal phase to 2-10 mass%. 9, 12, 13, and 18 to 20), the mechanical strength (three-point bending strength) is 327 MPa or more, the relative dielectric constant at 60 GHz is 7.9 or less, and the dielectric loss tangent (tan δ) at the same frequency is 28 × 10 ^{−. 4} or less, the rate of change in weight when chemical resistance was evaluated was 0.09% by mass or less.

Furthermore, in the samples (sample Nos. 3-5, 9, 13, and 18-20) in which the proportion of the canoite-based crystal phase is limited to 2-7 mass%, the mechanical strength (three-point bending strength) is 327 MPa or more, The relative dielectric constant at 60 GHz was 7.8 or less and the dielectric loss tangent was 18 × 10 ⁻⁴ or less with the weight change rate when evaluating the chemical properties maintained at 0.09% by mass or less.

  On the other hand, the samples (samples Nos. 8, 15 and 17) which do not contain the mullite crystal phase or do not contain the canoite crystal phase have a relative dielectric constant of 9.3 at 60 GHz and are evaluated for chemical resistance. The weight change rate was 0.16% by mass or more.

DESCRIPTION OF SYMBOLS 1 ...... Main crystal phase 1a ... Alumina crystal phase 1b ... Mullite crystal phase 3 ... Grain boundary 5 ... Canoite crystal phase 7 ... Glass phase

Claims (4)

  A ceramic sintered body comprising a composite phase of an alumina crystal phase and a mullite crystal phase as a main crystal phase, and a cananoite-based crystal phase at a grain boundary of the main crystal phase.   The ceramic sintered body according to claim 1, wherein the alumina crystal phase is 31 to 66% by mass, the mullite crystal phase is 30 to 65% by mass, and the canoite-based crystal phase is 2 to 10% by mass.   The ceramic sintered body according to claim 1 or 2, wherein the alumina crystal phase is surrounded by the mullite crystal phase spreading in a matrix.   A wiring board comprising: an insulating base constituted by the ceramic sintered body according to claim 1; and a conductor layer provided on at least a surface of the insulating base.

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